Performance analysis of flexible hierarchical cellular systems with a bandwidth-efficient handoff scheme

In this paper, a bandwidth-efficient handoff strategy is proposed and analyzed for hierarchical cellular systems. Mobile subscribers are divided into two classes, i.e., low- and high-mobility subscribers. In our bandwidth-efficient handoff strategy, each of the originating and handoff calls of both slow and fast mobile subscribers first tries to get a channel in a microcell. Macrocells are overlaid over the microcells to handle overflowed calls. A call overflowed into a macrocell requests a take-back to the new microcell at each border crossing of the microcells. The request will be accommodated by the target microcell if there is any idle traffic channel in the cell. An analytical model is developed, and the most important performance measures such as the blocking probability of originating calls and the forced termination probability of calls are evaluated. It is shown through extensive comparisons with other candidate handoff strategies that if the total traffic load of the system is not very heavy, our scheme has the best bandwidth efficiency and can provide better quality of service for mobile subscribers without bringing too much processing expense to the system